The present invention relates to a variable valve timing control system for an engine of an automobile.
U.S. Pat. No. 4,535,731 discloses a system for automatically varying the timing of a camshaft relative to a drive shaft of an internal combustion engine. This system comprises an axially slidable splined sleeve which connects the camshaft to its drive pulley, and is operated by the engine hydraulic fluid in such a manner as to change the angular position of the camshaft by way of a valve controlled by an electromagnetic actuator. The sleeve is axially movable between two limit positions, one being set by a return spring, and the other being set by application of the hydraulic fluid. Thus, the angular position of the camshaft is adjustable to only two positions.
An object of the present invention is to provide a continuously variable valve timing system wherein the angular position of the camshaft is continuously varied.
A specific object of the present invention is to provide a continuously variable valve timing system wherein, without relying on a feedback control to change the level of the hydraulic fluid, the angular position of the camshaft is continuously varied.